I suspect a lot of the tools you mentioned also already treat hashes as strings, not as 160 bit numeric types. The entire front-end JS for GitHub, for example, just uses strings. That's what I'd do if I were writing IDE integrations and such too.

Secondly, the new format will likely still be a 160-bit numeric type, just calculated using a different hash algorithm (e.g. it might be the first 160 bits of the SHA256 result). The tools you mentioned likely don't have to calculate said hashes, they just display them. The entire GitHub front-end, for instance, just displays whatever is given to it; commit hashes are input data to it, not output data.